The present invention is more particularly applicable to the case where a utilization member which is to receive the output beam is independently moveable relative to the light source. The power source may be a fixed carbon dioxide laser, for example, of relatively large weight and bulk, and suitable for providing an infrared beam with enough power for welding a collar in a tube of a steam generator in a nuclear reactor. Because of its bulk, the source can only be installed outside the water box of the generator, i.e., at a distance from the location at which the power is required. The beam must thus be transported from the laser to a welding head which constitutes said utilization member and which is installed in the tube to be repaired, and alignment is therefore necessary. Between the source and the position of utilization, there are two obstacles to be overcome:
1/penetration into the water box; and
2/penetration into the tube in the bundle of tubes.
In a prior art arrangement, the path to be followed is split into three lengths so as to obtain two intermediate points which are in sight of each other and which are situated inside the water box. Devices referred to below respectively as the "emitter" and as the "receiver" are placed at these two points. The source-to-emitter and the receiver-to-weldhead paths are traversed by conventional arrangements, with the receiver-to-weldhead path running along the axis of the tube to be repaired and being capable of being defined relative to the receiver by pressing the receiver against a surface which is fixed to the tube.
There remains the problem of controlling the emitter and the receiver in such a manner as to obtain a properly aligned outlet beam.
A system for providing such alignment is disclosed, for example, in EP-A-238171. This prior system includes a certain number of arrangements which, with respect to their functions mentioned below, are common to said system and to certain systems in accordance with the present invention, which common dispositions may be initially identified in general:
an emitter for receiving main power radiation and for transmitting it in the form of a main link beam controllable in direction to enable it to be directed towards a moveable receiver;
said receiver being adapted, when usefully receiving said main link beam, for transmitting it in the form of a main outlet beam and for causing a controllable angular deflection to appear between said two beams;
a moveable carrier carrying said receiver and controllable in position in order to control the position of said main outlet beam;
positioning means controlling the position of said carrier in order to bring said receiver onto a utilization axis on which the power of said main outlet beam is to be used; and
optical aiming means comprising:
an auxiliary source for generating auxiliary radiation transmitted by said emitter in the form of an auxiliary link beam having the same direction as said main link beam;
emitter control means sensitive to the irradiation of said receiver by a portion of said auxiliary radiation in order to control said emitter in such a manner that said auxiliary beam and said main link beam are directed towards said receiver;
a receiver mirror associated with said receiver for reflecting the remaining portion of said auxiliary radiation towards said emitter in the form of a return beam whose direction depends on said angular deflection of the receiver; and
receiver control means associated with said emitter and sensitive to the direction error of said return beam relative to said link beams in order to control said receiver in such a manner as to cause it to receive said main link beam usefully and to form said main outlet beam along said utilization axis.
This prior system described in EP-A-238171 suffers from the following drawbacks:
fragile equipment such as detectors, sensors, and video cameras are used in the hostile environment which surrounds the receiver;
implementation is discontinuous;
alignment must be performed each time the tube being treated is changed;
mechanical complexity; and
high cost.